It's good news for Americans that want to change wireless operators -- but only until 2015.

President Barack Obama today (Aug. 1) signed a bill into law that gives U.S. mobile phone users the right to unlock their mobile phones.

Obama signed the "Unlocking Consumer Choice and Wireless Competition Act" (S.517) that restores U.S. consumers' rights to update the software on their mobile phones so they can change mobile operators.

Like Us on Facebook

The law is good news for customers of AT&T and T-Mobile who will be able to quickly switch their unlocked mobile phones. It also benefits international travelers that want to buy service from a foreign carrier instead of roaming, which is usually more expensive.

There is, however, a bit of bad news for mobile phone users in the new law. Their right to unlock will expire in 2015.

That's when the exemption to the law that made unlocking possible in the first place is due for a review.

Unlocking mobile phones was outlawed by a January 2012 decision by the Library of Congress, which ruled that consumer unlocking violated the Digital Millennium Copyright Act (DMCA).

The Library of Congress ruled that changing software on a mobile phone violated the anti-circumvention provisions of the DMCA, which exists to prevent abuse of digital-rights-management technology.

Practically all mobile phones sold in the U.S. come with built-in software that locks the phone so it can be used on only one carrier's network.

The new law signed by Obama repeals the 2012 decision by the Library of Congress and makes unlocking a mobile phone legal again.

In 2013, the Library of Congress opted not to renew the DMCA exemption for mobile phone unlocking that it granted in 2006 and 2010.

Many politicians and consumer groups said the new law will help promote consumer choice in the wireless market. Tech experts warned, however, the reality is that the benefits might be slightly overstated since there are still huge technical barriers to taking any mobile phone to any wireless carrier in the US.

Unlocking doesn't actually mean what it means, said experts.

"Even though the vast majority of Americans enjoy upgrading to new devices once their contract terms are fulfilled, we recognize that some consumers may want to unlock their devices to move to another carrier," said Jot Carpenter, vice president of government affairs at CTIA.

"Like the voluntary commitment CTIA's carriers entered into last December, this bill enables that process. Users should keep in mind unlocked does not necessarily mean interoperable, as carrier platforms and spectrum holdings vary."

CTIA is the wireless industry's lobbying group.

Earlier this year, the Federal Communications Commission took the lead in a deal with major wireless carriers to allow consumers to unlock their mobile phones.

"This new law is a positive development that addresses the issues that triggered unlocking concerns in the first place," said FCC Chairman Tom Wheeler.

"When the wireless industry worked with the FCC on a voluntary agreement to unlock devices when consumers' contracts have been fulfilled, they took an important step forward. The president's signature today makes greater consumer choice the law of the land."